1. Field of the Invention
This invention relates to the diagnosis of abnormal & conditions in the lungs by conducting bronchoalveolar lavage. More particularly the present invention relates to a method and system for effecting and confirming proper wedging of the distal tip of a bronchoalveolar lavage catheter in a bronchiole of a lung of a patient.
2. Background Art
The technique of bronchoalveolar lavage has become common in the diagnosis of infections and other abnormalities in the alveoli at the terminus of the bronchioles in the lungs of a patient. In bronchoalveolar lavage (BAL), a sterile fluid is infused in aliquots of about 30 ml. each through the upper respiratory system of a patient into the portion of the lungs thereof designated for study. The fluid infused is then aspirated, cultured, and examined in order to isolate and identify infections, fungi, cells, and other signs of inflammation thusly flushed from the walls of the alveoli. Only about 40 to 60% of each infused aliquot can be aspirated. Thus in studies which require large volumes of aspirated fluid, a total infusion of from 30 to about 500 ml. may be required. A helpful background statement on the nature and useful findings related to the use of bronchoalveolar lavage is the American Thoracic Society, "Clinical Role of Bronchoalveolar Lavage in Adults with Pulmonary Disease", 142 AMERICAN REVIEW OF RESPIRATORY DISEASE, 481-486 (1990).
In order to effect the infusion of solution, it has in the past been the practice to utilize a bronchoscope to visually observe the advancement of a catheter through the upper respiratory system of a patient and the branching of the bronchi into a selected bronchiole. During this advancement process, the size of the air passage through which the distal tip of the bronchoscope is advanced gradually decreases until the distal tip of the bronchoscope wedges within the walls of a single bronchiole. This wedge is visually inspected using the bronchoscope, and thereafter the infusion and aspiration of solution is effected through a working lumen in the bronchoscope.
Drawbacks arise, however, in relation to the use of a bronchoscope in this procedure. First, the bronchoscope itself is a very expensive piece of equipment. As a result, it is not practical to dispose of the device following a single use. Instead, the bronchoscope must be reused in order to distribute its expense over a number of procedures. Routine heat-based sterilization, however, cannot be used. Instead, procedures must be employed which are particularly adapted to the delicate nature of the materials comprising the bronchoscope. These sterilization procedures require approximately twenty-four hours to complete, so that a single costly bronchoscope can be utilized at a given medical establishment only once a day. Thus, a plurality of bronchoscopes must be maintained by a medical establishment, if bronchoalveolar lavage is to be performed more than once a day.
In addition to being extremely delicate in the face of normal sterilization conditions, bronchoscopes are very susceptible to breakage through incorrect use. Like the device itself, repairs on the bronchoscope are extremely expensive. A reference discussing the sources of damage to flexible fiber optic bronchoscopes is Mehta, et al., "The High Price of Bronchoscopy: Maintenance and Repair of the Flexible Fiber Optic Bronchoscope," 98 CHEST 448-54 (August 1984).
Recent literature has forecast a rise in the frequency with which medical practitioners can be expected to resort to the use of bronchoalveolar lavage. The increased incidence of acquired immune deficiency syndrome (AIDS) and other therapeutic-related immunocompromising treatments, such as chemotherapy, gives rise to a large number of patients $ susceptible to multiple and exotic lung infections. An accurate diagnosis of the identity of these infections is essential, if the patient is to be effectively medicated. Typical of the literature discussing efforts at isolating lung infections in AIDS and other immunocompromised patients are the following:
Caughley, et al., "Non-Bronchoscopic Bronchio Alveoli Lavage for the Diagnosis of Pneumocystitis Carinii Pneumonia in the Acquired Immune Deficiency Syndrome", 88 CHEST 659-62 (November 1985). PA1 Sobonya, et al., "Detection of Fungi and other Pathogens in Immunocompromised Patients by Bronchio Alveoli Lavage in an Area Endemic for Coccidioidomycosis", 97 CHEST 1349-55 (June 1990).
Guerra, et al., "Use of Bronchio Alveoli Lavage to Diagnose Bacterial Pneumonia in Mechanically Ventilated Patients", 18 CRITICAL CARE MEDICINE, 169-73 (1990).
Some difficulties have also been experienced in effecting a clear diagnosis of conditions in the lung due to contamination of the equipment for conducting the bronchoalveolar lavage as the distal end of that equipment is passed through the upper respiratory system of a patient to the lung segment selected for study. In the process of that passage, the exterior of the distal end of the catheter by which infusion and aspiration is actually effected becomes contaminated with micro-organisms from the upper respiratory system of the patient. As a result, the fluid samples aspirated from the lungs thereafter are frequently compromised by cultures of organisms not actually located in the alveoli.
When a bronchoscope is not utilized, problems have been experienced in locating the distal tip of the sampling catheter in a specific preselected lung to be studied, placement in the left lung being particularly difficult due to inherent anatomical structure of the bronchi. Fluoroscopic and X-ray methods for verifying the location of a distal tip can to an extent be useful in assisting in directing the distal tip into a specific preselected lung. Nevertheless, these methods are totally incapable of replacing the primary value of bronchoscope use, namely the verification of distal tip wedging in a bronchiole of the patient to the extent required for successful infusion and aspiration of fluid. Fluoroscopic and X-ray methods for effecting placement are also complicated to utilize, and may be limited by availability to large medical institutions.
In conducting bronchoalveolar lavage several difficulties arise in effecting and verifying correct wedging of the distal tip of the catheter employed. In correct wedging, the walls of the bronchiole engage the full circumference of the resultant seal produces of the air passageways distal of the tip a closed space that permits optimal recovery of sampling fluid infused into those passageways. If the wedging of the distal tip of the bronchoalveolar lavage catheter has been correctly effected, these air passageways should be isolated from all others in the lung of the patient.
Correct wedging does not, however, result merely due to the advancement of a bronchoalveolar lavage catheter into the lung of a patient. In the absence of correct wedging, it is impossible to recover much or even any of the sampling fluid infused. Significant quantities of such fluid must be left in the lung of the patient after the procedure. Such non-aspirated sampling fluid can itself pose health hazards by stimulating pneumonia or other lung infections.
Ineffective wedging takes several forms. First, the shape or the orientation of the distal tip of the bronchoalveolar lavage catheter relative to the walls of the bronchiole in which it is lodged may be such that those walls do not engage the full circumference of the catheter tip. Under such circumstances, the air passageways distal of the wedging site are not isolated from the rest of the lungs, and the suction required for withdrawing the sampling solution cannot be effected. In addition, excess sampling solution injected into those air passageways can escape therefrom between the catheter tip and the bronchiole walls, thereby to settle in other portions of the lung than the portion upon which testing is being conducted. This escaped fluid, as well as sampling fluid not recovered from the targeted portion of the lung, presents the health hazards described already.
Where bronchoalveolar lavage is conducted without using a bronchoscope, it is common to attempt to confirm wedging merely from physical resistance to the advancement of the bronchoalveolar lavage catheter. Nevertheless, as appreciated from the discussion of ineffective wedging, it is possible for advancement of a bronchoalveolar lavage catheter to be precluded, but without securing a full circumferential seal on the distal tip of the catheter.
There are other circumstances in which one may be unable to recover the infused sampling fluid. For example, a full circumferential seal about the catheter tip may be effected by the walls of a bronchiole, but the action of respiration may cause one wall of the bronchiole, or even some other structure, to be drawn against the aperture opening into the lumen of the catheter through the distal tip thereof. Typically, this is most likely to occur when the aperture in the tip is disposed close to a wall of the bronchiole. Whenever this occurs, it is predictable that sampling fluid, if infused, could not then be aspirated. The sampling fluid would thus remain in the lungs. As used herein and in the appendant claims, the blocking of the opening into the distal tip of a bronchoalveolar lavage catheter in the manner described will be referred to as an "overwedged" condition.
Overwedging also occurs with regularity where the distal tip of the bronchoalveolar lavage catheter fails to negotiate a branching in the air passageway in which it is being advanced. This can result in precluded wedging, but in many instances the tissue in the space between the two branches of the air passageway directly enters the aperture through the tip of the catheter and then blocks the withdrawal of infused sampling fluid. The positive pressure of the infused sampling fluid nevertheless pushes aside the soft tissue of the bronchiole wall, so that fluid is admitted into the contiguous air passageways. In this respect, overwedging creates the functional equivalent of a one-way valve, which unfortunately enables a medical practitioner to fill a portion of the lung with fluid which cannot be removed.
It is possible using bronchoscopy to detect these types of overwedging, but bronchoscopy adds substantially to the cost of conducting bronchoalveolar lavage. Thus, while the creation of an overwedged condition can be expected with some degree of regularity, only through the use of expensive bronchoscopy will some of such conditions be detected before a full aliquot of ultimately unrecoverable sampling fluid is infused into the lungs.